The present invention relates to a method and apparatus for controlling the position of a grinding tool. A specific embodiment of the invention is implemented in an apparatus for grinding the edge of a glass sheet mounted on a rotary table.
An apparatus of this type is described in patent document EP 0 084 506 which is incorporated herein by reference. In that document, position control of the grinding tool is achieved by a positioning motor controlled by a sensor that scans the edge of the glass sheet ahead of the grinding tool. The sensor provides control signals which are stored in a shift register and used as set points to an adjustment amplifier when the rotary table has traveled the angular distance between the points of contact of the glass sheet with the scanning sensor and the grinding tool With such a grinding machine, this angular distance must initially be traversed by the sensor to program the shift register before the grinding operation starts. As a result, the total time of a grinding cycle is increased by the time necessary for this prior programming. Moreover, such a grinding machine necessitates the use of an edge sensor.